Journal of Power Sources 184 (2008) 265–275 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour H 2 production from CH 4 decomposition: Regeneration capability and performance of nickel and rhodium oxide catalysts M.E. Rivas a , C.E. Hori b , J.L.G. Fierro a,∗ , M.R. Goldwasser c , A. Griboval-Constant d a Instituto de Catálisis y Petroleoquímica, CSIC, Marie Curie n ◦ 2, Cantoblanco, 28049 Madrid, Spain b Faculdade de Engenharia Química, Universidade Federal de Uberlândia, Av. João Naves de Ávila 2121, Campus Santa Mônica, Bloco 1K, 38400-902 Uberlândia, MG, Brazil c Centro de Catálisis Petróleo y Petroquímica, Escuela de Química, Facultad de Ciencias, Universidad Central de Venezuela, Apartado 47102, Los Chaguaramos, Caracas, Venezuela d Unité de Catalyse et Chimie du Solide, UMR CNRS 8181, U.S.T.L., Bâtiment C3, 59655, Villeneuve D’Ascq, Cedex, France article info Article history: Received 13 March 2008 Received in revised form 3 June 2008 Accepted 4 June 2008 Available online 8 June 2008 Keywords: Ni–Rh perovskite precursors Methane decomposition Hydrogen production Characterization of catalysts abstract Nickel–lanthanum (LaNiO 3 ) and nickel–rhodium–lanthanum (LaNi 0.95 Rh 0.05 O 3 ) perovskite-type oxide precursors were synthesized by different methodologies (co-precipitation, sol–gel and impregnation). They were reduced in an H 2 atmosphere to produce nickel and rhodium nanoparticles on the La 2 O 3 sub- strate. All samples were tested in the catalytic decomposition of CH 4 . Methane decomposed into carbon and H 2 at reaction temperatures as low as 450 ◦ C—no other reaction products were observed. Conver- sions were in the range of 14–28%, and LaNi 0.95 Rh 0.05 O 3 synthesized by co-precipitation was the most active catalyst. All catalysts maintained sustained activity even after massive carbon deposition indi- cating that these deposits are of the nanotube-type, as confirmed by transmission electron microscopy (TEM). The reaction seems to occur in a way that a nickel or rhodium crystal face is always clean enough to expose sufficient active sites to make the catalytic process continue. The samples were subjected to a reduction–oxidation–reduction cycle and in situ analyses confirmed the stability of the perovskite struc- ture. All diffraction patterns showed a phase change around 400 ◦ C, due to reduction of LaNiO 3 to an intermediate La 2 Ni 2 O 5 structure. When the reduction temperatures reach 600 ◦ C, this structure collapses through the formation of Ni 0 crystallites deposited on the La 2 O 3 . Under oxidative conditions, the per- ovskite system is recomposed with nickel re-entering the LaNiO 3 framework structure accounting for the regenerative capability of these solids. © 2008 Elsevier B.V. All rights reserved. 1. Introduction The catalytic decomposition of methane (CDM) shows a promis- ing alternative to the traditional methods of hydrogen production, such as methane steam reforming (MSR) and partial oxidation of methane (POM) [1,2]. Due to the absence of oxygen, the forma- tion of carbon oxides is completely prevented in this process, and the need for additional downstream reactions, such as water–gas shift and selective oxidation, is eliminated. Moreover, the mixture of hydrogen and methane obtained from the CDM process could be directly used to feed internal combustion engines or gas tur- bine power plants [3], thus lowering the hydrogen production costs. Methane decomposition is a moderately endothermic process that requires 45.1 kJ mol -1 of H 2 produced at 800 ◦ C [4]. CH 4 → C + 2H 2 H 800 ◦ C =+ 90.1 kJ mol -1 (1) ∗ Corresponding author. Tel.: +34 91 585 4769; fax: +34 91 585 4767. E-mail address: jlgfierro@icp.csic.es (J.L.G. Fierro). Besides hydrogen, a CDM process also yields deposited carbon. The process requires not only a metal catalyst (Ni, Co, Fe and Pt) able to break the C–H bonds of the methane molecule, but also one that is able to maintain a high and sustained activity for a long time. On nickel catalysts, the carbon is usually deposited as nanofibers, which have several potential applications, such as electronic com- ponents, polymer additives, catalyst or catalyst support. In addition, this kind of carbon allows the catalyst to maintain its activity for an extended period of time without deactivation. Nickel is considered to be the most efficient metal, since it catalyzes the decomposi- tion of methane forming carbon nanofibers under relative mild conditions [5–8]. The stability and activity of Ni catalysts for CDM reaction depend on its textural properties and surface structure. A review of the results reported in literature shows that the morpho- logical appearance of the deposited carbon and the kinetics of CDM are affected by the nature of the active sites of the catalyst [9], the structure of the catalytic system, the textural properties and the size of the catalyst particles [10], the nature of the support [11,12], and the operating conditions, including the concentration of methane in the feed [13] and the reactor flow rate [14]. CDM reaction needs 0378-7753/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2008.06.002